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TOMOYO Linux Cross Reference
Linux/include/net/tcp.h

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  1 /*
  2  * INET         An implementation of the TCP/IP protocol suite for the LINUX
  3  *              operating system.  INET is implemented using the  BSD Socket
  4  *              interface as the means of communication with the user level.
  5  *
  6  *              Definitions for the TCP module.
  7  *
  8  * Version:     @(#)tcp.h       1.0.5   05/23/93
  9  *
 10  * Authors:     Ross Biro
 11  *              Fred N. van Kempen, <waltje@uWalt.NL.Mugnet.ORG>
 12  *
 13  *              This program is free software; you can redistribute it and/or
 14  *              modify it under the terms of the GNU General Public License
 15  *              as published by the Free Software Foundation; either version
 16  *              2 of the License, or (at your option) any later version.
 17  */
 18 #ifndef _TCP_H
 19 #define _TCP_H
 20 
 21 #define FASTRETRANS_DEBUG 1
 22 
 23 #include <linux/list.h>
 24 #include <linux/tcp.h>
 25 #include <linux/bug.h>
 26 #include <linux/slab.h>
 27 #include <linux/cache.h>
 28 #include <linux/percpu.h>
 29 #include <linux/skbuff.h>
 30 #include <linux/crypto.h>
 31 #include <linux/cryptohash.h>
 32 #include <linux/kref.h>
 33 #include <linux/ktime.h>
 34 
 35 #include <net/inet_connection_sock.h>
 36 #include <net/inet_timewait_sock.h>
 37 #include <net/inet_hashtables.h>
 38 #include <net/checksum.h>
 39 #include <net/request_sock.h>
 40 #include <net/sock.h>
 41 #include <net/snmp.h>
 42 #include <net/ip.h>
 43 #include <net/tcp_states.h>
 44 #include <net/inet_ecn.h>
 45 #include <net/dst.h>
 46 
 47 #include <linux/seq_file.h>
 48 #include <linux/memcontrol.h>
 49 
 50 extern struct inet_hashinfo tcp_hashinfo;
 51 
 52 extern struct percpu_counter tcp_orphan_count;
 53 void tcp_time_wait(struct sock *sk, int state, int timeo);
 54 
 55 #define MAX_TCP_HEADER  (128 + MAX_HEADER)
 56 #define MAX_TCP_OPTION_SPACE 40
 57 
 58 /*
 59  * Never offer a window over 32767 without using window scaling. Some
 60  * poor stacks do signed 16bit maths!
 61  */
 62 #define MAX_TCP_WINDOW          32767U
 63 
 64 /* Minimal accepted MSS. It is (60+60+8) - (20+20). */
 65 #define TCP_MIN_MSS             88U
 66 
 67 /* The least MTU to use for probing */
 68 #define TCP_BASE_MSS            1024
 69 
 70 /* probing interval, default to 10 minutes as per RFC4821 */
 71 #define TCP_PROBE_INTERVAL      600
 72 
 73 /* Specify interval when tcp mtu probing will stop */
 74 #define TCP_PROBE_THRESHOLD     8
 75 
 76 /* After receiving this amount of duplicate ACKs fast retransmit starts. */
 77 #define TCP_FASTRETRANS_THRESH 3
 78 
 79 /* Maximal number of ACKs sent quickly to accelerate slow-start. */
 80 #define TCP_MAX_QUICKACKS       16U
 81 
 82 /* urg_data states */
 83 #define TCP_URG_VALID   0x0100
 84 #define TCP_URG_NOTYET  0x0200
 85 #define TCP_URG_READ    0x0400
 86 
 87 #define TCP_RETR1       3       /*
 88                                  * This is how many retries it does before it
 89                                  * tries to figure out if the gateway is
 90                                  * down. Minimal RFC value is 3; it corresponds
 91                                  * to ~3sec-8min depending on RTO.
 92                                  */
 93 
 94 #define TCP_RETR2       15      /*
 95                                  * This should take at least
 96                                  * 90 minutes to time out.
 97                                  * RFC1122 says that the limit is 100 sec.
 98                                  * 15 is ~13-30min depending on RTO.
 99                                  */
100 
101 #define TCP_SYN_RETRIES  6      /* This is how many retries are done
102                                  * when active opening a connection.
103                                  * RFC1122 says the minimum retry MUST
104                                  * be at least 180secs.  Nevertheless
105                                  * this value is corresponding to
106                                  * 63secs of retransmission with the
107                                  * current initial RTO.
108                                  */
109 
110 #define TCP_SYNACK_RETRIES 5    /* This is how may retries are done
111                                  * when passive opening a connection.
112                                  * This is corresponding to 31secs of
113                                  * retransmission with the current
114                                  * initial RTO.
115                                  */
116 
117 #define TCP_TIMEWAIT_LEN (60*HZ) /* how long to wait to destroy TIME-WAIT
118                                   * state, about 60 seconds     */
119 #define TCP_FIN_TIMEOUT TCP_TIMEWAIT_LEN
120                                  /* BSD style FIN_WAIT2 deadlock breaker.
121                                   * It used to be 3min, new value is 60sec,
122                                   * to combine FIN-WAIT-2 timeout with
123                                   * TIME-WAIT timer.
124                                   */
125 
126 #define TCP_DELACK_MAX  ((unsigned)(HZ/5))      /* maximal time to delay before sending an ACK */
127 #if HZ >= 100
128 #define TCP_DELACK_MIN  ((unsigned)(HZ/25))     /* minimal time to delay before sending an ACK */
129 #define TCP_ATO_MIN     ((unsigned)(HZ/25))
130 #else
131 #define TCP_DELACK_MIN  4U
132 #define TCP_ATO_MIN     4U
133 #endif
134 #define TCP_RTO_MAX     ((unsigned)(120*HZ))
135 #define TCP_RTO_MIN     ((unsigned)(HZ/5))
136 #define TCP_TIMEOUT_INIT ((unsigned)(1*HZ))     /* RFC6298 2.1 initial RTO value        */
137 #define TCP_TIMEOUT_FALLBACK ((unsigned)(3*HZ)) /* RFC 1122 initial RTO value, now
138                                                  * used as a fallback RTO for the
139                                                  * initial data transmission if no
140                                                  * valid RTT sample has been acquired,
141                                                  * most likely due to retrans in 3WHS.
142                                                  */
143 
144 #define TCP_RESOURCE_PROBE_INTERVAL ((unsigned)(HZ/2U)) /* Maximal interval between probes
145                                                          * for local resources.
146                                                          */
147 
148 #define TCP_KEEPALIVE_TIME      (120*60*HZ)     /* two hours */
149 #define TCP_KEEPALIVE_PROBES    9               /* Max of 9 keepalive probes    */
150 #define TCP_KEEPALIVE_INTVL     (75*HZ)
151 
152 #define MAX_TCP_KEEPIDLE        32767
153 #define MAX_TCP_KEEPINTVL       32767
154 #define MAX_TCP_KEEPCNT         127
155 #define MAX_TCP_SYNCNT          127
156 
157 #define TCP_SYNQ_INTERVAL       (HZ/5)  /* Period of SYNACK timer */
158 
159 #define TCP_PAWS_24DAYS (60 * 60 * 24 * 24)
160 #define TCP_PAWS_MSL    60              /* Per-host timestamps are invalidated
161                                          * after this time. It should be equal
162                                          * (or greater than) TCP_TIMEWAIT_LEN
163                                          * to provide reliability equal to one
164                                          * provided by timewait state.
165                                          */
166 #define TCP_PAWS_WINDOW 1               /* Replay window for per-host
167                                          * timestamps. It must be less than
168                                          * minimal timewait lifetime.
169                                          */
170 /*
171  *      TCP option
172  */
173 
174 #define TCPOPT_NOP              1       /* Padding */
175 #define TCPOPT_EOL              0       /* End of options */
176 #define TCPOPT_MSS              2       /* Segment size negotiating */
177 #define TCPOPT_WINDOW           3       /* Window scaling */
178 #define TCPOPT_SACK_PERM        4       /* SACK Permitted */
179 #define TCPOPT_SACK             5       /* SACK Block */
180 #define TCPOPT_TIMESTAMP        8       /* Better RTT estimations/PAWS */
181 #define TCPOPT_MD5SIG           19      /* MD5 Signature (RFC2385) */
182 #define TCPOPT_FASTOPEN         34      /* Fast open (RFC7413) */
183 #define TCPOPT_EXP              254     /* Experimental */
184 /* Magic number to be after the option value for sharing TCP
185  * experimental options. See draft-ietf-tcpm-experimental-options-00.txt
186  */
187 #define TCPOPT_FASTOPEN_MAGIC   0xF989
188 
189 /*
190  *     TCP option lengths
191  */
192 
193 #define TCPOLEN_MSS            4
194 #define TCPOLEN_WINDOW         3
195 #define TCPOLEN_SACK_PERM      2
196 #define TCPOLEN_TIMESTAMP      10
197 #define TCPOLEN_MD5SIG         18
198 #define TCPOLEN_FASTOPEN_BASE  2
199 #define TCPOLEN_EXP_FASTOPEN_BASE  4
200 
201 /* But this is what stacks really send out. */
202 #define TCPOLEN_TSTAMP_ALIGNED          12
203 #define TCPOLEN_WSCALE_ALIGNED          4
204 #define TCPOLEN_SACKPERM_ALIGNED        4
205 #define TCPOLEN_SACK_BASE               2
206 #define TCPOLEN_SACK_BASE_ALIGNED       4
207 #define TCPOLEN_SACK_PERBLOCK           8
208 #define TCPOLEN_MD5SIG_ALIGNED          20
209 #define TCPOLEN_MSS_ALIGNED             4
210 
211 /* Flags in tp->nonagle */
212 #define TCP_NAGLE_OFF           1       /* Nagle's algo is disabled */
213 #define TCP_NAGLE_CORK          2       /* Socket is corked         */
214 #define TCP_NAGLE_PUSH          4       /* Cork is overridden for already queued data */
215 
216 /* TCP thin-stream limits */
217 #define TCP_THIN_LINEAR_RETRIES 6       /* After 6 linear retries, do exp. backoff */
218 
219 /* TCP initial congestion window as per draft-hkchu-tcpm-initcwnd-01 */
220 #define TCP_INIT_CWND           10
221 
222 /* Bit Flags for sysctl_tcp_fastopen */
223 #define TFO_CLIENT_ENABLE       1
224 #define TFO_SERVER_ENABLE       2
225 #define TFO_CLIENT_NO_COOKIE    4       /* Data in SYN w/o cookie option */
226 
227 /* Accept SYN data w/o any cookie option */
228 #define TFO_SERVER_COOKIE_NOT_REQD      0x200
229 
230 /* Force enable TFO on all listeners, i.e., not requiring the
231  * TCP_FASTOPEN socket option. SOCKOPT1/2 determine how to set max_qlen.
232  */
233 #define TFO_SERVER_WO_SOCKOPT1  0x400
234 #define TFO_SERVER_WO_SOCKOPT2  0x800
235 
236 extern struct inet_timewait_death_row tcp_death_row;
237 
238 /* sysctl variables for tcp */
239 extern int sysctl_tcp_timestamps;
240 extern int sysctl_tcp_window_scaling;
241 extern int sysctl_tcp_sack;
242 extern int sysctl_tcp_fin_timeout;
243 extern int sysctl_tcp_keepalive_time;
244 extern int sysctl_tcp_keepalive_probes;
245 extern int sysctl_tcp_keepalive_intvl;
246 extern int sysctl_tcp_syn_retries;
247 extern int sysctl_tcp_synack_retries;
248 extern int sysctl_tcp_retries1;
249 extern int sysctl_tcp_retries2;
250 extern int sysctl_tcp_orphan_retries;
251 extern int sysctl_tcp_syncookies;
252 extern int sysctl_tcp_fastopen;
253 extern int sysctl_tcp_retrans_collapse;
254 extern int sysctl_tcp_stdurg;
255 extern int sysctl_tcp_rfc1337;
256 extern int sysctl_tcp_abort_on_overflow;
257 extern int sysctl_tcp_max_orphans;
258 extern int sysctl_tcp_fack;
259 extern int sysctl_tcp_reordering;
260 extern int sysctl_tcp_max_reordering;
261 extern int sysctl_tcp_dsack;
262 extern long sysctl_tcp_mem[3];
263 extern int sysctl_tcp_wmem[3];
264 extern int sysctl_tcp_rmem[3];
265 extern int sysctl_tcp_app_win;
266 extern int sysctl_tcp_adv_win_scale;
267 extern int sysctl_tcp_tw_reuse;
268 extern int sysctl_tcp_frto;
269 extern int sysctl_tcp_low_latency;
270 extern int sysctl_tcp_nometrics_save;
271 extern int sysctl_tcp_moderate_rcvbuf;
272 extern int sysctl_tcp_tso_win_divisor;
273 extern int sysctl_tcp_workaround_signed_windows;
274 extern int sysctl_tcp_slow_start_after_idle;
275 extern int sysctl_tcp_thin_linear_timeouts;
276 extern int sysctl_tcp_thin_dupack;
277 extern int sysctl_tcp_early_retrans;
278 extern int sysctl_tcp_limit_output_bytes;
279 extern int sysctl_tcp_challenge_ack_limit;
280 extern unsigned int sysctl_tcp_notsent_lowat;
281 extern int sysctl_tcp_min_tso_segs;
282 extern int sysctl_tcp_autocorking;
283 extern int sysctl_tcp_invalid_ratelimit;
284 extern int sysctl_tcp_pacing_ss_ratio;
285 extern int sysctl_tcp_pacing_ca_ratio;
286 
287 extern atomic_long_t tcp_memory_allocated;
288 extern struct percpu_counter tcp_sockets_allocated;
289 extern int tcp_memory_pressure;
290 
291 /* optimized version of sk_under_memory_pressure() for TCP sockets */
292 static inline bool tcp_under_memory_pressure(const struct sock *sk)
293 {
294         if (mem_cgroup_sockets_enabled && sk->sk_cgrp)
295                 return !!sk->sk_cgrp->memory_pressure;
296 
297         return tcp_memory_pressure;
298 }
299 /*
300  * The next routines deal with comparing 32 bit unsigned ints
301  * and worry about wraparound (automatic with unsigned arithmetic).
302  */
303 
304 static inline bool before(__u32 seq1, __u32 seq2)
305 {
306         return (__s32)(seq1-seq2) < 0;
307 }
308 #define after(seq2, seq1)       before(seq1, seq2)
309 
310 /* is s2<=s1<=s3 ? */
311 static inline bool between(__u32 seq1, __u32 seq2, __u32 seq3)
312 {
313         return seq3 - seq2 >= seq1 - seq2;
314 }
315 
316 static inline bool tcp_out_of_memory(struct sock *sk)
317 {
318         if (sk->sk_wmem_queued > SOCK_MIN_SNDBUF &&
319             sk_memory_allocated(sk) > sk_prot_mem_limits(sk, 2))
320                 return true;
321         return false;
322 }
323 
324 void sk_forced_mem_schedule(struct sock *sk, int size);
325 
326 static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
327 {
328         struct percpu_counter *ocp = sk->sk_prot->orphan_count;
329         int orphans = percpu_counter_read_positive(ocp);
330 
331         if (orphans << shift > sysctl_tcp_max_orphans) {
332                 orphans = percpu_counter_sum_positive(ocp);
333                 if (orphans << shift > sysctl_tcp_max_orphans)
334                         return true;
335         }
336         return false;
337 }
338 
339 bool tcp_check_oom(struct sock *sk, int shift);
340 
341 
342 extern struct proto tcp_prot;
343 
344 #define TCP_INC_STATS(net, field)       SNMP_INC_STATS((net)->mib.tcp_statistics, field)
345 #define TCP_INC_STATS_BH(net, field)    SNMP_INC_STATS_BH((net)->mib.tcp_statistics, field)
346 #define TCP_DEC_STATS(net, field)       SNMP_DEC_STATS((net)->mib.tcp_statistics, field)
347 #define TCP_ADD_STATS_USER(net, field, val) SNMP_ADD_STATS_USER((net)->mib.tcp_statistics, field, val)
348 #define TCP_ADD_STATS(net, field, val)  SNMP_ADD_STATS((net)->mib.tcp_statistics, field, val)
349 
350 void tcp_tasklet_init(void);
351 
352 void tcp_v4_err(struct sk_buff *skb, u32);
353 
354 void tcp_shutdown(struct sock *sk, int how);
355 
356 void tcp_v4_early_demux(struct sk_buff *skb);
357 int tcp_v4_rcv(struct sk_buff *skb);
358 
359 int tcp_v4_tw_remember_stamp(struct inet_timewait_sock *tw);
360 int tcp_sendmsg(struct sock *sk, struct msghdr *msg, size_t size);
361 int tcp_sendpage(struct sock *sk, struct page *page, int offset, size_t size,
362                  int flags);
363 void tcp_release_cb(struct sock *sk);
364 void tcp_wfree(struct sk_buff *skb);
365 void tcp_write_timer_handler(struct sock *sk);
366 void tcp_delack_timer_handler(struct sock *sk);
367 int tcp_ioctl(struct sock *sk, int cmd, unsigned long arg);
368 int tcp_rcv_state_process(struct sock *sk, struct sk_buff *skb,
369                           const struct tcphdr *th, unsigned int len);
370 void tcp_rcv_established(struct sock *sk, struct sk_buff *skb,
371                          const struct tcphdr *th, unsigned int len);
372 void tcp_rcv_space_adjust(struct sock *sk);
373 int tcp_twsk_unique(struct sock *sk, struct sock *sktw, void *twp);
374 void tcp_twsk_destructor(struct sock *sk);
375 ssize_t tcp_splice_read(struct socket *sk, loff_t *ppos,
376                         struct pipe_inode_info *pipe, size_t len,
377                         unsigned int flags);
378 
379 static inline void tcp_dec_quickack_mode(struct sock *sk,
380                                          const unsigned int pkts)
381 {
382         struct inet_connection_sock *icsk = inet_csk(sk);
383 
384         if (icsk->icsk_ack.quick) {
385                 if (pkts >= icsk->icsk_ack.quick) {
386                         icsk->icsk_ack.quick = 0;
387                         /* Leaving quickack mode we deflate ATO. */
388                         icsk->icsk_ack.ato   = TCP_ATO_MIN;
389                 } else
390                         icsk->icsk_ack.quick -= pkts;
391         }
392 }
393 
394 #define TCP_ECN_OK              1
395 #define TCP_ECN_QUEUE_CWR       2
396 #define TCP_ECN_DEMAND_CWR      4
397 #define TCP_ECN_SEEN            8
398 
399 enum tcp_tw_status {
400         TCP_TW_SUCCESS = 0,
401         TCP_TW_RST = 1,
402         TCP_TW_ACK = 2,
403         TCP_TW_SYN = 3
404 };
405 
406 
407 enum tcp_tw_status tcp_timewait_state_process(struct inet_timewait_sock *tw,
408                                               struct sk_buff *skb,
409                                               const struct tcphdr *th);
410 struct sock *tcp_check_req(struct sock *sk, struct sk_buff *skb,
411                            struct request_sock *req, bool fastopen);
412 int tcp_child_process(struct sock *parent, struct sock *child,
413                       struct sk_buff *skb);
414 void tcp_enter_loss(struct sock *sk);
415 void tcp_clear_retrans(struct tcp_sock *tp);
416 void tcp_update_metrics(struct sock *sk);
417 void tcp_init_metrics(struct sock *sk);
418 void tcp_metrics_init(void);
419 bool tcp_peer_is_proven(struct request_sock *req, struct dst_entry *dst,
420                         bool paws_check, bool timestamps);
421 bool tcp_remember_stamp(struct sock *sk);
422 bool tcp_tw_remember_stamp(struct inet_timewait_sock *tw);
423 void tcp_fetch_timewait_stamp(struct sock *sk, struct dst_entry *dst);
424 void tcp_disable_fack(struct tcp_sock *tp);
425 void tcp_close(struct sock *sk, long timeout);
426 void tcp_init_sock(struct sock *sk);
427 unsigned int tcp_poll(struct file *file, struct socket *sock,
428                       struct poll_table_struct *wait);
429 int tcp_getsockopt(struct sock *sk, int level, int optname,
430                    char __user *optval, int __user *optlen);
431 int tcp_setsockopt(struct sock *sk, int level, int optname,
432                    char __user *optval, unsigned int optlen);
433 int compat_tcp_getsockopt(struct sock *sk, int level, int optname,
434                           char __user *optval, int __user *optlen);
435 int compat_tcp_setsockopt(struct sock *sk, int level, int optname,
436                           char __user *optval, unsigned int optlen);
437 void tcp_set_keepalive(struct sock *sk, int val);
438 void tcp_syn_ack_timeout(const struct request_sock *req);
439 int tcp_recvmsg(struct sock *sk, struct msghdr *msg, size_t len, int nonblock,
440                 int flags, int *addr_len);
441 void tcp_parse_options(const struct sk_buff *skb,
442                        struct tcp_options_received *opt_rx,
443                        int estab, struct tcp_fastopen_cookie *foc);
444 const u8 *tcp_parse_md5sig_option(const struct tcphdr *th);
445 
446 /*
447  *      TCP v4 functions exported for the inet6 API
448  */
449 
450 void tcp_v4_send_check(struct sock *sk, struct sk_buff *skb);
451 void tcp_v4_mtu_reduced(struct sock *sk);
452 void tcp_req_err(struct sock *sk, u32 seq);
453 int tcp_v4_conn_request(struct sock *sk, struct sk_buff *skb);
454 struct sock *tcp_create_openreq_child(struct sock *sk,
455                                       struct request_sock *req,
456                                       struct sk_buff *skb);
457 void tcp_ca_openreq_child(struct sock *sk, const struct dst_entry *dst);
458 struct sock *tcp_v4_syn_recv_sock(struct sock *sk, struct sk_buff *skb,
459                                   struct request_sock *req,
460                                   struct dst_entry *dst);
461 int tcp_v4_do_rcv(struct sock *sk, struct sk_buff *skb);
462 int tcp_v4_connect(struct sock *sk, struct sockaddr *uaddr, int addr_len);
463 int tcp_connect(struct sock *sk);
464 struct sk_buff *tcp_make_synack(struct sock *sk, struct dst_entry *dst,
465                                 struct request_sock *req,
466                                 struct tcp_fastopen_cookie *foc);
467 int tcp_disconnect(struct sock *sk, int flags);
468 
469 void tcp_finish_connect(struct sock *sk, struct sk_buff *skb);
470 int tcp_send_rcvq(struct sock *sk, struct msghdr *msg, size_t size);
471 void inet_sk_rx_dst_set(struct sock *sk, const struct sk_buff *skb);
472 
473 /* From syncookies.c */
474 struct sock *tcp_get_cookie_sock(struct sock *sk, struct sk_buff *skb,
475                                  struct request_sock *req,
476                                  struct dst_entry *dst);
477 int __cookie_v4_check(const struct iphdr *iph, const struct tcphdr *th,
478                       u32 cookie);
479 struct sock *cookie_v4_check(struct sock *sk, struct sk_buff *skb);
480 #ifdef CONFIG_SYN_COOKIES
481 
482 /* Syncookies use a monotonic timer which increments every 60 seconds.
483  * This counter is used both as a hash input and partially encoded into
484  * the cookie value.  A cookie is only validated further if the delta
485  * between the current counter value and the encoded one is less than this,
486  * i.e. a sent cookie is valid only at most for 2*60 seconds (or less if
487  * the counter advances immediately after a cookie is generated).
488  */
489 #define MAX_SYNCOOKIE_AGE       2
490 #define TCP_SYNCOOKIE_PERIOD    (60 * HZ)
491 #define TCP_SYNCOOKIE_VALID     (MAX_SYNCOOKIE_AGE * TCP_SYNCOOKIE_PERIOD)
492 
493 /* syncookies: remember time of last synqueue overflow
494  * But do not dirty this field too often (once per second is enough)
495  */
496 static inline void tcp_synq_overflow(struct sock *sk)
497 {
498         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
499         unsigned long now = jiffies;
500 
501         if (time_after(now, last_overflow + HZ))
502                 tcp_sk(sk)->rx_opt.ts_recent_stamp = now;
503 }
504 
505 /* syncookies: no recent synqueue overflow on this listening socket? */
506 static inline bool tcp_synq_no_recent_overflow(const struct sock *sk)
507 {
508         unsigned long last_overflow = tcp_sk(sk)->rx_opt.ts_recent_stamp;
509 
510         return time_after(jiffies, last_overflow + TCP_SYNCOOKIE_VALID);
511 }
512 
513 static inline u32 tcp_cookie_time(void)
514 {
515         u64 val = get_jiffies_64();
516 
517         do_div(val, TCP_SYNCOOKIE_PERIOD);
518         return val;
519 }
520 
521 u32 __cookie_v4_init_sequence(const struct iphdr *iph, const struct tcphdr *th,
522                               u16 *mssp);
523 __u32 cookie_v4_init_sequence(struct sock *sk, const struct sk_buff *skb,
524                               __u16 *mss);
525 __u32 cookie_init_timestamp(struct request_sock *req);
526 bool cookie_timestamp_decode(struct tcp_options_received *opt);
527 bool cookie_ecn_ok(const struct tcp_options_received *opt,
528                    const struct net *net, const struct dst_entry *dst);
529 
530 /* From net/ipv6/syncookies.c */
531 int __cookie_v6_check(const struct ipv6hdr *iph, const struct tcphdr *th,
532                       u32 cookie);
533 struct sock *cookie_v6_check(struct sock *sk, struct sk_buff *skb);
534 
535 u32 __cookie_v6_init_sequence(const struct ipv6hdr *iph,
536                               const struct tcphdr *th, u16 *mssp);
537 __u32 cookie_v6_init_sequence(struct sock *sk, const struct sk_buff *skb,
538                               __u16 *mss);
539 #endif
540 /* tcp_output.c */
541 
542 void __tcp_push_pending_frames(struct sock *sk, unsigned int cur_mss,
543                                int nonagle);
544 bool tcp_may_send_now(struct sock *sk);
545 int __tcp_retransmit_skb(struct sock *, struct sk_buff *);
546 int tcp_retransmit_skb(struct sock *, struct sk_buff *);
547 void tcp_retransmit_timer(struct sock *sk);
548 void tcp_xmit_retransmit_queue(struct sock *);
549 void tcp_simple_retransmit(struct sock *);
550 int tcp_trim_head(struct sock *, struct sk_buff *, u32);
551 int tcp_fragment(struct sock *, struct sk_buff *, u32, unsigned int, gfp_t);
552 
553 void tcp_send_probe0(struct sock *);
554 void tcp_send_partial(struct sock *);
555 int tcp_write_wakeup(struct sock *, int mib);
556 void tcp_send_fin(struct sock *sk);
557 void tcp_send_active_reset(struct sock *sk, gfp_t priority);
558 int tcp_send_synack(struct sock *);
559 void tcp_push_one(struct sock *, unsigned int mss_now);
560 void tcp_send_ack(struct sock *sk);
561 void tcp_send_delayed_ack(struct sock *sk);
562 void tcp_send_loss_probe(struct sock *sk);
563 bool tcp_schedule_loss_probe(struct sock *sk);
564 
565 /* tcp_input.c */
566 void tcp_resume_early_retransmit(struct sock *sk);
567 void tcp_rearm_rto(struct sock *sk);
568 void tcp_reset(struct sock *sk);
569 
570 /* tcp_timer.c */
571 void tcp_init_xmit_timers(struct sock *);
572 static inline void tcp_clear_xmit_timers(struct sock *sk)
573 {
574         inet_csk_clear_xmit_timers(sk);
575 }
576 
577 unsigned int tcp_sync_mss(struct sock *sk, u32 pmtu);
578 unsigned int tcp_current_mss(struct sock *sk);
579 
580 /* Bound MSS / TSO packet size with the half of the window */
581 static inline int tcp_bound_to_half_wnd(struct tcp_sock *tp, int pktsize)
582 {
583         int cutoff;
584 
585         /* When peer uses tiny windows, there is no use in packetizing
586          * to sub-MSS pieces for the sake of SWS or making sure there
587          * are enough packets in the pipe for fast recovery.
588          *
589          * On the other hand, for extremely large MSS devices, handling
590          * smaller than MSS windows in this way does make sense.
591          */
592         if (tp->max_window >= 512)
593                 cutoff = (tp->max_window >> 1);
594         else
595                 cutoff = tp->max_window;
596 
597         if (cutoff && pktsize > cutoff)
598                 return max_t(int, cutoff, 68U - tp->tcp_header_len);
599         else
600                 return pktsize;
601 }
602 
603 /* tcp.c */
604 void tcp_get_info(struct sock *, struct tcp_info *);
605 
606 /* Read 'sendfile()'-style from a TCP socket */
607 typedef int (*sk_read_actor_t)(read_descriptor_t *, struct sk_buff *,
608                                 unsigned int, size_t);
609 int tcp_read_sock(struct sock *sk, read_descriptor_t *desc,
610                   sk_read_actor_t recv_actor);
611 
612 void tcp_initialize_rcv_mss(struct sock *sk);
613 
614 int tcp_mtu_to_mss(struct sock *sk, int pmtu);
615 int tcp_mss_to_mtu(struct sock *sk, int mss);
616 void tcp_mtup_init(struct sock *sk);
617 void tcp_init_buffer_space(struct sock *sk);
618 
619 static inline void tcp_bound_rto(const struct sock *sk)
620 {
621         if (inet_csk(sk)->icsk_rto > TCP_RTO_MAX)
622                 inet_csk(sk)->icsk_rto = TCP_RTO_MAX;
623 }
624 
625 static inline u32 __tcp_set_rto(const struct tcp_sock *tp)
626 {
627         return usecs_to_jiffies((tp->srtt_us >> 3) + tp->rttvar_us);
628 }
629 
630 static inline void __tcp_fast_path_on(struct tcp_sock *tp, u32 snd_wnd)
631 {
632         tp->pred_flags = htonl((tp->tcp_header_len << 26) |
633                                ntohl(TCP_FLAG_ACK) |
634                                snd_wnd);
635 }
636 
637 static inline void tcp_fast_path_on(struct tcp_sock *tp)
638 {
639         __tcp_fast_path_on(tp, tp->snd_wnd >> tp->rx_opt.snd_wscale);
640 }
641 
642 static inline void tcp_fast_path_check(struct sock *sk)
643 {
644         struct tcp_sock *tp = tcp_sk(sk);
645 
646         if (skb_queue_empty(&tp->out_of_order_queue) &&
647             tp->rcv_wnd &&
648             atomic_read(&sk->sk_rmem_alloc) < sk->sk_rcvbuf &&
649             !tp->urg_data)
650                 tcp_fast_path_on(tp);
651 }
652 
653 /* Compute the actual rto_min value */
654 static inline u32 tcp_rto_min(struct sock *sk)
655 {
656         const struct dst_entry *dst = __sk_dst_get(sk);
657         u32 rto_min = TCP_RTO_MIN;
658 
659         if (dst && dst_metric_locked(dst, RTAX_RTO_MIN))
660                 rto_min = dst_metric_rtt(dst, RTAX_RTO_MIN);
661         return rto_min;
662 }
663 
664 static inline u32 tcp_rto_min_us(struct sock *sk)
665 {
666         return jiffies_to_usecs(tcp_rto_min(sk));
667 }
668 
669 static inline bool tcp_ca_dst_locked(const struct dst_entry *dst)
670 {
671         return dst_metric_locked(dst, RTAX_CC_ALGO);
672 }
673 
674 /* Compute the actual receive window we are currently advertising.
675  * Rcv_nxt can be after the window if our peer push more data
676  * than the offered window.
677  */
678 static inline u32 tcp_receive_window(const struct tcp_sock *tp)
679 {
680         s32 win = tp->rcv_wup + tp->rcv_wnd - tp->rcv_nxt;
681 
682         if (win < 0)
683                 win = 0;
684         return (u32) win;
685 }
686 
687 /* Choose a new window, without checks for shrinking, and without
688  * scaling applied to the result.  The caller does these things
689  * if necessary.  This is a "raw" window selection.
690  */
691 u32 __tcp_select_window(struct sock *sk);
692 
693 void tcp_send_window_probe(struct sock *sk);
694 
695 /* TCP timestamps are only 32-bits, this causes a slight
696  * complication on 64-bit systems since we store a snapshot
697  * of jiffies in the buffer control blocks below.  We decided
698  * to use only the low 32-bits of jiffies and hide the ugly
699  * casts with the following macro.
700  */
701 #define tcp_time_stamp          ((__u32)(jiffies))
702 
703 static inline u32 tcp_skb_timestamp(const struct sk_buff *skb)
704 {
705         return skb->skb_mstamp.stamp_jiffies;
706 }
707 
708 
709 #define tcp_flag_byte(th) (((u_int8_t *)th)[13])
710 
711 #define TCPHDR_FIN 0x01
712 #define TCPHDR_SYN 0x02
713 #define TCPHDR_RST 0x04
714 #define TCPHDR_PSH 0x08
715 #define TCPHDR_ACK 0x10
716 #define TCPHDR_URG 0x20
717 #define TCPHDR_ECE 0x40
718 #define TCPHDR_CWR 0x80
719 
720 #define TCPHDR_SYN_ECN  (TCPHDR_SYN | TCPHDR_ECE | TCPHDR_CWR)
721 
722 /* This is what the send packet queuing engine uses to pass
723  * TCP per-packet control information to the transmission code.
724  * We also store the host-order sequence numbers in here too.
725  * This is 44 bytes if IPV6 is enabled.
726  * If this grows please adjust skbuff.h:skbuff->cb[xxx] size appropriately.
727  */
728 struct tcp_skb_cb {
729         __u32           seq;            /* Starting sequence number     */
730         __u32           end_seq;        /* SEQ + FIN + SYN + datalen    */
731         union {
732                 /* Note : tcp_tw_isn is used in input path only
733                  *        (isn chosen by tcp_timewait_state_process())
734                  *
735                  *        tcp_gso_segs/size are used in write queue only,
736                  *        cf tcp_skb_pcount()/tcp_skb_mss()
737                  */
738                 __u32           tcp_tw_isn;
739                 struct {
740                         u16     tcp_gso_segs;
741                         u16     tcp_gso_size;
742                 };
743         };
744         __u8            tcp_flags;      /* TCP header flags. (tcp[13])  */
745 
746         __u8            sacked;         /* State flags for SACK/FACK.   */
747 #define TCPCB_SACKED_ACKED      0x01    /* SKB ACK'd by a SACK block    */
748 #define TCPCB_SACKED_RETRANS    0x02    /* SKB retransmitted            */
749 #define TCPCB_LOST              0x04    /* SKB is lost                  */
750 #define TCPCB_TAGBITS           0x07    /* All tag bits                 */
751 #define TCPCB_REPAIRED          0x10    /* SKB repaired (no skb_mstamp) */
752 #define TCPCB_EVER_RETRANS      0x80    /* Ever retransmitted frame     */
753 #define TCPCB_RETRANS           (TCPCB_SACKED_RETRANS|TCPCB_EVER_RETRANS| \
754                                 TCPCB_REPAIRED)
755 
756         __u8            ip_dsfield;     /* IPv4 tos or IPv6 dsfield     */
757         /* 1 byte hole */
758         __u32           ack_seq;        /* Sequence number ACK'd        */
759         union {
760                 struct inet_skb_parm    h4;
761 #if IS_ENABLED(CONFIG_IPV6)
762                 struct inet6_skb_parm   h6;
763 #endif
764         } header;       /* For incoming frames          */
765 };
766 
767 #define TCP_SKB_CB(__skb)       ((struct tcp_skb_cb *)&((__skb)->cb[0]))
768 
769 
770 #if IS_ENABLED(CONFIG_IPV6)
771 /* This is the variant of inet6_iif() that must be used by TCP,
772  * as TCP moves IP6CB into a different location in skb->cb[]
773  */
774 static inline int tcp_v6_iif(const struct sk_buff *skb)
775 {
776         return TCP_SKB_CB(skb)->header.h6.iif;
777 }
778 #endif
779 
780 /* Due to TSO, an SKB can be composed of multiple actual
781  * packets.  To keep these tracked properly, we use this.
782  */
783 static inline int tcp_skb_pcount(const struct sk_buff *skb)
784 {
785         return TCP_SKB_CB(skb)->tcp_gso_segs;
786 }
787 
788 static inline void tcp_skb_pcount_set(struct sk_buff *skb, int segs)
789 {
790         TCP_SKB_CB(skb)->tcp_gso_segs = segs;
791 }
792 
793 static inline void tcp_skb_pcount_add(struct sk_buff *skb, int segs)
794 {
795         TCP_SKB_CB(skb)->tcp_gso_segs += segs;
796 }
797 
798 /* This is valid iff skb is in write queue and tcp_skb_pcount() > 1. */
799 static inline int tcp_skb_mss(const struct sk_buff *skb)
800 {
801         return TCP_SKB_CB(skb)->tcp_gso_size;
802 }
803 
804 /* Events passed to congestion control interface */
805 enum tcp_ca_event {
806         CA_EVENT_TX_START,      /* first transmit when no packets in flight */
807         CA_EVENT_CWND_RESTART,  /* congestion window restart */
808         CA_EVENT_COMPLETE_CWR,  /* end of congestion recovery */
809         CA_EVENT_LOSS,          /* loss timeout */
810         CA_EVENT_ECN_NO_CE,     /* ECT set, but not CE marked */
811         CA_EVENT_ECN_IS_CE,     /* received CE marked IP packet */
812         CA_EVENT_DELAYED_ACK,   /* Delayed ack is sent */
813         CA_EVENT_NON_DELAYED_ACK,
814 };
815 
816 /* Information about inbound ACK, passed to cong_ops->in_ack_event() */
817 enum tcp_ca_ack_event_flags {
818         CA_ACK_SLOWPATH         = (1 << 0),     /* In slow path processing */
819         CA_ACK_WIN_UPDATE       = (1 << 1),     /* ACK updated window */
820         CA_ACK_ECE              = (1 << 2),     /* ECE bit is set on ack */
821 };
822 
823 /*
824  * Interface for adding new TCP congestion control handlers
825  */
826 #define TCP_CA_NAME_MAX 16
827 #define TCP_CA_MAX      128
828 #define TCP_CA_BUF_MAX  (TCP_CA_NAME_MAX*TCP_CA_MAX)
829 
830 #define TCP_CA_UNSPEC   0
831 
832 /* Algorithm can be set on socket without CAP_NET_ADMIN privileges */
833 #define TCP_CONG_NON_RESTRICTED 0x1
834 /* Requires ECN/ECT set on all packets */
835 #define TCP_CONG_NEEDS_ECN      0x2
836 
837 union tcp_cc_info;
838 
839 struct tcp_congestion_ops {
840         struct list_head        list;
841         u32 key;
842         u32 flags;
843 
844         /* initialize private data (optional) */
845         void (*init)(struct sock *sk);
846         /* cleanup private data  (optional) */
847         void (*release)(struct sock *sk);
848 
849         /* return slow start threshold (required) */
850         u32 (*ssthresh)(struct sock *sk);
851         /* do new cwnd calculation (required) */
852         void (*cong_avoid)(struct sock *sk, u32 ack, u32 acked);
853         /* call before changing ca_state (optional) */
854         void (*set_state)(struct sock *sk, u8 new_state);
855         /* call when cwnd event occurs (optional) */
856         void (*cwnd_event)(struct sock *sk, enum tcp_ca_event ev);
857         /* call when ack arrives (optional) */
858         void (*in_ack_event)(struct sock *sk, u32 flags);
859         /* new value of cwnd after loss (optional) */
860         u32  (*undo_cwnd)(struct sock *sk);
861         /* hook for packet ack accounting (optional) */
862         void (*pkts_acked)(struct sock *sk, u32 num_acked, s32 rtt_us);
863         /* get info for inet_diag (optional) */
864         size_t (*get_info)(struct sock *sk, u32 ext, int *attr,
865                            union tcp_cc_info *info);
866 
867         char            name[TCP_CA_NAME_MAX];
868         struct module   *owner;
869 };
870 
871 int tcp_register_congestion_control(struct tcp_congestion_ops *type);
872 void tcp_unregister_congestion_control(struct tcp_congestion_ops *type);
873 
874 void tcp_assign_congestion_control(struct sock *sk);
875 void tcp_init_congestion_control(struct sock *sk);
876 void tcp_cleanup_congestion_control(struct sock *sk);
877 int tcp_set_default_congestion_control(const char *name);
878 void tcp_get_default_congestion_control(char *name);
879 void tcp_get_available_congestion_control(char *buf, size_t len);
880 void tcp_get_allowed_congestion_control(char *buf, size_t len);
881 int tcp_set_allowed_congestion_control(char *allowed);
882 int tcp_set_congestion_control(struct sock *sk, const char *name);
883 u32 tcp_slow_start(struct tcp_sock *tp, u32 acked);
884 void tcp_cong_avoid_ai(struct tcp_sock *tp, u32 w, u32 acked);
885 
886 u32 tcp_reno_ssthresh(struct sock *sk);
887 void tcp_reno_cong_avoid(struct sock *sk, u32 ack, u32 acked);
888 extern struct tcp_congestion_ops tcp_reno;
889 
890 struct tcp_congestion_ops *tcp_ca_find_key(u32 key);
891 u32 tcp_ca_get_key_by_name(const char *name, bool *ecn_ca);
892 #ifdef CONFIG_INET
893 char *tcp_ca_get_name_by_key(u32 key, char *buffer);
894 #else
895 static inline char *tcp_ca_get_name_by_key(u32 key, char *buffer)
896 {
897         return NULL;
898 }
899 #endif
900 
901 static inline bool tcp_ca_needs_ecn(const struct sock *sk)
902 {
903         const struct inet_connection_sock *icsk = inet_csk(sk);
904 
905         return icsk->icsk_ca_ops->flags & TCP_CONG_NEEDS_ECN;
906 }
907 
908 static inline void tcp_set_ca_state(struct sock *sk, const u8 ca_state)
909 {
910         struct inet_connection_sock *icsk = inet_csk(sk);
911 
912         if (icsk->icsk_ca_ops->set_state)
913                 icsk->icsk_ca_ops->set_state(sk, ca_state);
914         icsk->icsk_ca_state = ca_state;
915 }
916 
917 static inline void tcp_ca_event(struct sock *sk, const enum tcp_ca_event event)
918 {
919         const struct inet_connection_sock *icsk = inet_csk(sk);
920 
921         if (icsk->icsk_ca_ops->cwnd_event)
922                 icsk->icsk_ca_ops->cwnd_event(sk, event);
923 }
924 
925 /* These functions determine how the current flow behaves in respect of SACK
926  * handling. SACK is negotiated with the peer, and therefore it can vary
927  * between different flows.
928  *
929  * tcp_is_sack - SACK enabled
930  * tcp_is_reno - No SACK
931  * tcp_is_fack - FACK enabled, implies SACK enabled
932  */
933 static inline int tcp_is_sack(const struct tcp_sock *tp)
934 {
935         return tp->rx_opt.sack_ok;
936 }
937 
938 static inline bool tcp_is_reno(const struct tcp_sock *tp)
939 {
940         return !tcp_is_sack(tp);
941 }
942 
943 static inline bool tcp_is_fack(const struct tcp_sock *tp)
944 {
945         return tp->rx_opt.sack_ok & TCP_FACK_ENABLED;
946 }
947 
948 static inline void tcp_enable_fack(struct tcp_sock *tp)
949 {
950         tp->rx_opt.sack_ok |= TCP_FACK_ENABLED;
951 }
952 
953 /* TCP early-retransmit (ER) is similar to but more conservative than
954  * the thin-dupack feature.  Enable ER only if thin-dupack is disabled.
955  */
956 static inline void tcp_enable_early_retrans(struct tcp_sock *tp)
957 {
958         tp->do_early_retrans = sysctl_tcp_early_retrans &&
959                 sysctl_tcp_early_retrans < 4 && !sysctl_tcp_thin_dupack &&
960                 sysctl_tcp_reordering == 3;
961 }
962 
963 static inline void tcp_disable_early_retrans(struct tcp_sock *tp)
964 {
965         tp->do_early_retrans = 0;
966 }
967 
968 static inline unsigned int tcp_left_out(const struct tcp_sock *tp)
969 {
970         return tp->sacked_out + tp->lost_out;
971 }
972 
973 /* This determines how many packets are "in the network" to the best
974  * of our knowledge.  In many cases it is conservative, but where
975  * detailed information is available from the receiver (via SACK
976  * blocks etc.) we can make more aggressive calculations.
977  *
978  * Use this for decisions involving congestion control, use just
979  * tp->packets_out to determine if the send queue is empty or not.
980  *
981  * Read this equation as:
982  *
983  *      "Packets sent once on transmission queue" MINUS
984  *      "Packets left network, but not honestly ACKed yet" PLUS
985  *      "Packets fast retransmitted"
986  */
987 static inline unsigned int tcp_packets_in_flight(const struct tcp_sock *tp)
988 {
989         return tp->packets_out - tcp_left_out(tp) + tp->retrans_out;
990 }
991 
992 #define TCP_INFINITE_SSTHRESH   0x7fffffff
993 
994 static inline bool tcp_in_slow_start(const struct tcp_sock *tp)
995 {
996         return tp->snd_cwnd < tp->snd_ssthresh;
997 }
998 
999 static inline bool tcp_in_initial_slowstart(const struct tcp_sock *tp)
1000 {
1001         return tp->snd_ssthresh >= TCP_INFINITE_SSTHRESH;
1002 }
1003 
1004 static inline bool tcp_in_cwnd_reduction(const struct sock *sk)
1005 {
1006         return (TCPF_CA_CWR | TCPF_CA_Recovery) &
1007                (1 << inet_csk(sk)->icsk_ca_state);
1008 }
1009 
1010 /* If cwnd > ssthresh, we may raise ssthresh to be half-way to cwnd.
1011  * The exception is cwnd reduction phase, when cwnd is decreasing towards
1012  * ssthresh.
1013  */
1014 static inline __u32 tcp_current_ssthresh(const struct sock *sk)
1015 {
1016         const struct tcp_sock *tp = tcp_sk(sk);
1017 
1018         if (tcp_in_cwnd_reduction(sk))
1019                 return tp->snd_ssthresh;
1020         else
1021                 return max(tp->snd_ssthresh,
1022                            ((tp->snd_cwnd >> 1) +
1023                             (tp->snd_cwnd >> 2)));
1024 }
1025 
1026 /* Use define here intentionally to get WARN_ON location shown at the caller */
1027 #define tcp_verify_left_out(tp) WARN_ON(tcp_left_out(tp) > tp->packets_out)
1028 
1029 void tcp_enter_cwr(struct sock *sk);
1030 __u32 tcp_init_cwnd(const struct tcp_sock *tp, const struct dst_entry *dst);
1031 
1032 /* The maximum number of MSS of available cwnd for which TSO defers
1033  * sending if not using sysctl_tcp_tso_win_divisor.
1034  */
1035 static inline __u32 tcp_max_tso_deferred_mss(const struct tcp_sock *tp)
1036 {
1037         return 3;
1038 }
1039 
1040 /* Slow start with delack produces 3 packets of burst, so that
1041  * it is safe "de facto".  This will be the default - same as
1042  * the default reordering threshold - but if reordering increases,
1043  * we must be able to allow cwnd to burst at least this much in order
1044  * to not pull it back when holes are filled.
1045  */
1046 static __inline__ __u32 tcp_max_burst(const struct tcp_sock *tp)
1047 {
1048         return tp->reordering;
1049 }
1050 
1051 /* Returns end sequence number of the receiver's advertised window */
1052 static inline u32 tcp_wnd_end(const struct tcp_sock *tp)
1053 {
1054         return tp->snd_una + tp->snd_wnd;
1055 }
1056 
1057 /* We follow the spirit of RFC2861 to validate cwnd but implement a more
1058  * flexible approach. The RFC suggests cwnd should not be raised unless
1059  * it was fully used previously. And that's exactly what we do in
1060  * congestion avoidance mode. But in slow start we allow cwnd to grow
1061  * as long as the application has used half the cwnd.
1062  * Example :
1063  *    cwnd is 10 (IW10), but application sends 9 frames.
1064  *    We allow cwnd to reach 18 when all frames are ACKed.
1065  * This check is safe because it's as aggressive as slow start which already
1066  * risks 100% overshoot. The advantage is that we discourage application to
1067  * either send more filler packets or data to artificially blow up the cwnd
1068  * usage, and allow application-limited process to probe bw more aggressively.
1069  */
1070 static inline bool tcp_is_cwnd_limited(const struct sock *sk)
1071 {
1072         const struct tcp_sock *tp = tcp_sk(sk);
1073 
1074         /* If in slow start, ensure cwnd grows to twice what was ACKed. */
1075         if (tcp_in_slow_start(tp))
1076                 return tp->snd_cwnd < 2 * tp->max_packets_out;
1077 
1078         return tp->is_cwnd_limited;
1079 }
1080 
1081 /* Something is really bad, we could not queue an additional packet,
1082  * because qdisc is full or receiver sent a 0 window.
1083  * We do not want to add fuel to the fire, or abort too early,
1084  * so make sure the timer we arm now is at least 200ms in the future,
1085  * regardless of current icsk_rto value (as it could be ~2ms)
1086  */
1087 static inline unsigned long tcp_probe0_base(const struct sock *sk)
1088 {
1089         return max_t(unsigned long, inet_csk(sk)->icsk_rto, TCP_RTO_MIN);
1090 }
1091 
1092 /* Variant of inet_csk_rto_backoff() used for zero window probes */
1093 static inline unsigned long tcp_probe0_when(const struct sock *sk,
1094                                             unsigned long max_when)
1095 {
1096         u64 when = (u64)tcp_probe0_base(sk) << inet_csk(sk)->icsk_backoff;
1097 
1098         return (unsigned long)min_t(u64, when, max_when);
1099 }
1100 
1101 static inline void tcp_check_probe_timer(struct sock *sk)
1102 {
1103         if (!tcp_sk(sk)->packets_out && !inet_csk(sk)->icsk_pending)
1104                 inet_csk_reset_xmit_timer(sk, ICSK_TIME_PROBE0,
1105                                           tcp_probe0_base(sk), TCP_RTO_MAX);
1106 }
1107 
1108 static inline void tcp_init_wl(struct tcp_sock *tp, u32 seq)
1109 {
1110         tp->snd_wl1 = seq;
1111 }
1112 
1113 static inline void tcp_update_wl(struct tcp_sock *tp, u32 seq)
1114 {
1115         tp->snd_wl1 = seq;
1116 }
1117 
1118 /*
1119  * Calculate(/check) TCP checksum
1120  */
1121 static inline __sum16 tcp_v4_check(int len, __be32 saddr,
1122                                    __be32 daddr, __wsum base)
1123 {
1124         return csum_tcpudp_magic(saddr,daddr,len,IPPROTO_TCP,base);
1125 }
1126 
1127 static inline __sum16 __tcp_checksum_complete(struct sk_buff *skb)
1128 {
1129         return __skb_checksum_complete(skb);
1130 }
1131 
1132 static inline bool tcp_checksum_complete(struct sk_buff *skb)
1133 {
1134         return !skb_csum_unnecessary(skb) &&
1135                 __tcp_checksum_complete(skb);
1136 }
1137 
1138 /* Prequeue for VJ style copy to user, combined with checksumming. */
1139 
1140 static inline void tcp_prequeue_init(struct tcp_sock *tp)
1141 {
1142         tp->ucopy.task = NULL;
1143         tp->ucopy.len = 0;
1144         tp->ucopy.memory = 0;
1145         skb_queue_head_init(&tp->ucopy.prequeue);
1146 }
1147 
1148 bool tcp_prequeue(struct sock *sk, struct sk_buff *skb);
1149 
1150 #undef STATE_TRACE
1151 
1152 #ifdef STATE_TRACE
1153 static const char *statename[]={
1154         "Unused","Established","Syn Sent","Syn Recv",
1155         "Fin Wait 1","Fin Wait 2","Time Wait", "Close",
1156         "Close Wait","Last ACK","Listen","Closing"
1157 };
1158 #endif
1159 void tcp_set_state(struct sock *sk, int state);
1160 
1161 void tcp_done(struct sock *sk);
1162 
1163 static inline void tcp_sack_reset(struct tcp_options_received *rx_opt)
1164 {
1165         rx_opt->dsack = 0;
1166         rx_opt->num_sacks = 0;
1167 }
1168 
1169 u32 tcp_default_init_rwnd(u32 mss);
1170 void tcp_cwnd_restart(struct sock *sk, s32 delta);
1171 
1172 static inline void tcp_slow_start_after_idle_check(struct sock *sk)
1173 {
1174         struct tcp_sock *tp = tcp_sk(sk);
1175         s32 delta;
1176 
1177         if (!sysctl_tcp_slow_start_after_idle || tp->packets_out)
1178                 return;
1179         delta = tcp_time_stamp - tp->lsndtime;
1180         if (delta > inet_csk(sk)->icsk_rto)
1181                 tcp_cwnd_restart(sk, delta);
1182 }
1183 
1184 /* Determine a window scaling and initial window to offer. */
1185 void tcp_select_initial_window(int __space, __u32 mss, __u32 *rcv_wnd,
1186                                __u32 *window_clamp, int wscale_ok,
1187                                __u8 *rcv_wscale, __u32 init_rcv_wnd);
1188 
1189 static inline int tcp_win_from_space(int space)
1190 {
1191         return sysctl_tcp_adv_win_scale<=0 ?
1192                 (space>>(-sysctl_tcp_adv_win_scale)) :
1193                 space - (space>>sysctl_tcp_adv_win_scale);
1194 }
1195 
1196 /* Note: caller must be prepared to deal with negative returns */
1197 static inline int tcp_space(const struct sock *sk)
1198 {
1199         return tcp_win_from_space(sk->sk_rcvbuf -
1200                                   atomic_read(&sk->sk_rmem_alloc));
1201 }
1202 
1203 static inline int tcp_full_space(const struct sock *sk)
1204 {
1205         return tcp_win_from_space(sk->sk_rcvbuf);
1206 }
1207 
1208 extern void tcp_openreq_init_rwin(struct request_sock *req,
1209                                   struct sock *sk, struct dst_entry *dst);
1210 
1211 void tcp_enter_memory_pressure(struct sock *sk);
1212 
1213 static inline int keepalive_intvl_when(const struct tcp_sock *tp)
1214 {
1215         return tp->keepalive_intvl ? : sysctl_tcp_keepalive_intvl;
1216 }
1217 
1218 static inline int keepalive_time_when(const struct tcp_sock *tp)
1219 {
1220         return tp->keepalive_time ? : sysctl_tcp_keepalive_time;
1221 }
1222 
1223 static inline int keepalive_probes(const struct tcp_sock *tp)
1224 {
1225         return tp->keepalive_probes ? : sysctl_tcp_keepalive_probes;
1226 }
1227 
1228 static inline u32 keepalive_time_elapsed(const struct tcp_sock *tp)
1229 {
1230         const struct inet_connection_sock *icsk = &tp->inet_conn;
1231 
1232         return min_t(u32, tcp_time_stamp - icsk->icsk_ack.lrcvtime,
1233                           tcp_time_stamp - tp->rcv_tstamp);
1234 }
1235 
1236 static inline int tcp_fin_time(const struct sock *sk)
1237 {
1238         int fin_timeout = tcp_sk(sk)->linger2 ? : sysctl_tcp_fin_timeout;
1239         const int rto = inet_csk(sk)->icsk_rto;
1240 
1241         if (fin_timeout < (rto << 2) - (rto >> 1))
1242                 fin_timeout = (rto << 2) - (rto >> 1);
1243 
1244         return fin_timeout;
1245 }
1246 
1247 static inline bool tcp_paws_check(const struct tcp_options_received *rx_opt,
1248                                   int paws_win)
1249 {
1250         if ((s32)(rx_opt->ts_recent - rx_opt->rcv_tsval) <= paws_win)
1251                 return true;
1252         if (unlikely(get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_24DAYS))
1253                 return true;
1254         /*
1255          * Some OSes send SYN and SYNACK messages with tsval=0 tsecr=0,
1256          * then following tcp messages have valid values. Ignore 0 value,
1257          * or else 'negative' tsval might forbid us to accept their packets.
1258          */
1259         if (!rx_opt->ts_recent)
1260                 return true;
1261         return false;
1262 }
1263 
1264 static inline bool tcp_paws_reject(const struct tcp_options_received *rx_opt,
1265                                    int rst)
1266 {
1267         if (tcp_paws_check(rx_opt, 0))
1268                 return false;
1269 
1270         /* RST segments are not recommended to carry timestamp,
1271            and, if they do, it is recommended to ignore PAWS because
1272            "their cleanup function should take precedence over timestamps."
1273            Certainly, it is mistake. It is necessary to understand the reasons
1274            of this constraint to relax it: if peer reboots, clock may go
1275            out-of-sync and half-open connections will not be reset.
1276            Actually, the problem would be not existing if all
1277            the implementations followed draft about maintaining clock
1278            via reboots. Linux-2.2 DOES NOT!
1279 
1280            However, we can relax time bounds for RST segments to MSL.
1281          */
1282         if (rst && get_seconds() >= rx_opt->ts_recent_stamp + TCP_PAWS_MSL)
1283                 return false;
1284         return true;
1285 }
1286 
1287 bool tcp_oow_rate_limited(struct net *net, const struct sk_buff *skb,
1288                           int mib_idx, u32 *last_oow_ack_time);
1289 
1290 static inline void tcp_mib_init(struct net *net)
1291 {
1292         /* See RFC 2012 */
1293         TCP_ADD_STATS_USER(net, TCP_MIB_RTOALGORITHM, 1);
1294         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMIN, TCP_RTO_MIN*1000/HZ);
1295         TCP_ADD_STATS_USER(net, TCP_MIB_RTOMAX, TCP_RTO_MAX*1000/HZ);
1296         TCP_ADD_STATS_USER(net, TCP_MIB_MAXCONN, -1);
1297 }
1298 
1299 /* from STCP */
1300 static inline void tcp_clear_retrans_hints_partial(struct tcp_sock *tp)
1301 {
1302         tp->lost_skb_hint = NULL;
1303 }
1304 
1305 static inline void tcp_clear_all_retrans_hints(struct tcp_sock *tp)
1306 {
1307         tcp_clear_retrans_hints_partial(tp);
1308         tp->retransmit_skb_hint = NULL;
1309 }
1310 
1311 /* MD5 Signature */
1312 struct crypto_hash;
1313 
1314 union tcp_md5_addr {
1315         struct in_addr  a4;
1316 #if IS_ENABLED(CONFIG_IPV6)
1317         struct in6_addr a6;
1318 #endif
1319 };
1320 
1321 /* - key database */
1322 struct tcp_md5sig_key {
1323         struct hlist_node       node;
1324         u8                      keylen;
1325         u8                      family; /* AF_INET or AF_INET6 */
1326         union tcp_md5_addr      addr;
1327         u8                      key[TCP_MD5SIG_MAXKEYLEN];
1328         struct rcu_head         rcu;
1329 };
1330 
1331 /* - sock block */
1332 struct tcp_md5sig_info {
1333         struct hlist_head       head;
1334         struct rcu_head         rcu;
1335 };
1336 
1337 /* - pseudo header */
1338 struct tcp4_pseudohdr {
1339         __be32          saddr;
1340         __be32          daddr;
1341         __u8            pad;
1342         __u8            protocol;
1343         __be16          len;
1344 };
1345 
1346 struct tcp6_pseudohdr {
1347         struct in6_addr saddr;
1348         struct in6_addr daddr;
1349         __be32          len;
1350         __be32          protocol;       /* including padding */
1351 };
1352 
1353 union tcp_md5sum_block {
1354         struct tcp4_pseudohdr ip4;
1355 #if IS_ENABLED(CONFIG_IPV6)
1356         struct tcp6_pseudohdr ip6;
1357 #endif
1358 };
1359 
1360 /* - pool: digest algorithm, hash description and scratch buffer */
1361 struct tcp_md5sig_pool {
1362         struct hash_desc        md5_desc;
1363         union tcp_md5sum_block  md5_blk;
1364 };
1365 
1366 /* - functions */
1367 int tcp_v4_md5_hash_skb(char *md5_hash, const struct tcp_md5sig_key *key,
1368                         const struct sock *sk, const struct sk_buff *skb);
1369 int tcp_md5_do_add(struct sock *sk, const union tcp_md5_addr *addr,
1370                    int family, const u8 *newkey, u8 newkeylen, gfp_t gfp);
1371 int tcp_md5_do_del(struct sock *sk, const union tcp_md5_addr *addr,
1372                    int family);
1373 struct tcp_md5sig_key *tcp_v4_md5_lookup(struct sock *sk,
1374                                          const struct sock *addr_sk);
1375 
1376 #ifdef CONFIG_TCP_MD5SIG
1377 struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1378                                          const union tcp_md5_addr *addr,
1379                                          int family);
1380 #define tcp_twsk_md5_key(twsk)  ((twsk)->tw_md5_key)
1381 #else
1382 static inline struct tcp_md5sig_key *tcp_md5_do_lookup(struct sock *sk,
1383                                          const union tcp_md5_addr *addr,
1384                                          int family)
1385 {
1386         return NULL;
1387 }
1388 #define tcp_twsk_md5_key(twsk)  NULL
1389 #endif
1390 
1391 bool tcp_alloc_md5sig_pool(void);
1392 
1393 struct tcp_md5sig_pool *tcp_get_md5sig_pool(void);
1394 static inline void tcp_put_md5sig_pool(void)
1395 {
1396         local_bh_enable();
1397 }
1398 
1399 int tcp_md5_hash_header(struct tcp_md5sig_pool *, const struct tcphdr *);
1400 int tcp_md5_hash_skb_data(struct tcp_md5sig_pool *, const struct sk_buff *,
1401                           unsigned int header_len);
1402 int tcp_md5_hash_key(struct tcp_md5sig_pool *hp,
1403                      const struct tcp_md5sig_key *key);
1404 
1405 /* From tcp_fastopen.c */
1406 void tcp_fastopen_cache_get(struct sock *sk, u16 *mss,
1407                             struct tcp_fastopen_cookie *cookie, int *syn_loss,
1408                             unsigned long *last_syn_loss);
1409 void tcp_fastopen_cache_set(struct sock *sk, u16 mss,
1410                             struct tcp_fastopen_cookie *cookie, bool syn_lost,
1411                             u16 try_exp);
1412 struct tcp_fastopen_request {
1413         /* Fast Open cookie. Size 0 means a cookie request */
1414         struct tcp_fastopen_cookie      cookie;
1415         struct msghdr                   *data;  /* data in MSG_FASTOPEN */
1416         size_t                          size;
1417         int                             copied; /* queued in tcp_connect() */
1418 };
1419 void tcp_free_fastopen_req(struct tcp_sock *tp);
1420 
1421 extern struct tcp_fastopen_context __rcu *tcp_fastopen_ctx;
1422 int tcp_fastopen_reset_cipher(void *key, unsigned int len);
1423 bool tcp_try_fastopen(struct sock *sk, struct sk_buff *skb,
1424                       struct request_sock *req,
1425                       struct tcp_fastopen_cookie *foc,
1426                       struct dst_entry *dst);
1427 void tcp_fastopen_init_key_once(bool publish);
1428 #define TCP_FASTOPEN_KEY_LENGTH 16
1429 
1430 /* Fastopen key context */
1431 struct tcp_fastopen_context {
1432         struct crypto_cipher    *tfm;
1433         __u8                    key[TCP_FASTOPEN_KEY_LENGTH];
1434         struct rcu_head         rcu;
1435 };
1436 
1437 /* write queue abstraction */
1438 static inline void tcp_write_queue_purge(struct sock *sk)
1439 {
1440         struct sk_buff *skb;
1441 
1442         while ((skb = __skb_dequeue(&sk->sk_write_queue)) != NULL)
1443                 sk_wmem_free_skb(sk, skb);
1444         sk_mem_reclaim(sk);
1445         tcp_clear_all_retrans_hints(tcp_sk(sk));
1446 }
1447 
1448 static inline struct sk_buff *tcp_write_queue_head(const struct sock *sk)
1449 {
1450         return skb_peek(&sk->sk_write_queue);
1451 }
1452 
1453 static inline struct sk_buff *tcp_write_queue_tail(const struct sock *sk)
1454 {
1455         return skb_peek_tail(&sk->sk_write_queue);
1456 }
1457 
1458 static inline struct sk_buff *tcp_write_queue_next(const struct sock *sk,
1459                                                    const struct sk_buff *skb)
1460 {
1461         return skb_queue_next(&sk->sk_write_queue, skb);
1462 }
1463 
1464 static inline struct sk_buff *tcp_write_queue_prev(const struct sock *sk,
1465                                                    const struct sk_buff *skb)
1466 {
1467         return skb_queue_prev(&sk->sk_write_queue, skb);
1468 }
1469 
1470 #define tcp_for_write_queue(skb, sk)                                    \
1471         skb_queue_walk(&(sk)->sk_write_queue, skb)
1472 
1473 #define tcp_for_write_queue_from(skb, sk)                               \
1474         skb_queue_walk_from(&(sk)->sk_write_queue, skb)
1475 
1476 #define tcp_for_write_queue_from_safe(skb, tmp, sk)                     \
1477         skb_queue_walk_from_safe(&(sk)->sk_write_queue, skb, tmp)
1478 
1479 static inline struct sk_buff *tcp_send_head(const struct sock *sk)
1480 {
1481         return sk->sk_send_head;
1482 }
1483 
1484 static inline bool tcp_skb_is_last(const struct sock *sk,
1485                                    const struct sk_buff *skb)
1486 {
1487         return skb_queue_is_last(&sk->sk_write_queue, skb);
1488 }
1489 
1490 static inline void tcp_advance_send_head(struct sock *sk, const struct sk_buff *skb)
1491 {
1492         if (tcp_skb_is_last(sk, skb))
1493                 sk->sk_send_head = NULL;
1494         else
1495                 sk->sk_send_head = tcp_write_queue_next(sk, skb);
1496 }
1497 
1498 static inline void tcp_check_send_head(struct sock *sk, struct sk_buff *skb_unlinked)
1499 {
1500         if (sk->sk_send_head == skb_unlinked)
1501                 sk->sk_send_head = NULL;
1502 }
1503 
1504 static inline void tcp_init_send_head(struct sock *sk)
1505 {
1506         sk->sk_send_head = NULL;
1507 }
1508 
1509 static inline void __tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1510 {
1511         __skb_queue_tail(&sk->sk_write_queue, skb);
1512 }
1513 
1514 static inline void tcp_add_write_queue_tail(struct sock *sk, struct sk_buff *skb)
1515 {
1516         __tcp_add_write_queue_tail(sk, skb);
1517 
1518         /* Queue it, remembering where we must start sending. */
1519         if (sk->sk_send_head == NULL) {
1520                 sk->sk_send_head = skb;
1521 
1522                 if (tcp_sk(sk)->highest_sack == NULL)
1523                         tcp_sk(sk)->highest_sack = skb;
1524         }
1525 }
1526 
1527 static inline void __tcp_add_write_queue_head(struct sock *sk, struct sk_buff *skb)
1528 {
1529         __skb_queue_head(&sk->sk_write_queue, skb);
1530 }
1531 
1532 /* Insert buff after skb on the write queue of sk.  */
1533 static inline void tcp_insert_write_queue_after(struct sk_buff *skb,
1534                                                 struct sk_buff *buff,
1535                                                 struct sock *sk)
1536 {
1537         __skb_queue_after(&sk->sk_write_queue, skb, buff);
1538 }
1539 
1540 /* Insert new before skb on the write queue of sk.  */
1541 static inline void tcp_insert_write_queue_before(struct sk_buff *new,
1542                                                   struct sk_buff *skb,
1543                                                   struct sock *sk)
1544 {
1545         __skb_queue_before(&sk->sk_write_queue, skb, new);
1546 
1547         if (sk->sk_send_head == skb)
1548                 sk->sk_send_head = new;
1549 }
1550 
1551 static inline void tcp_unlink_write_queue(struct sk_buff *skb, struct sock *sk)
1552 {
1553         __skb_unlink(skb, &sk->sk_write_queue);
1554 }
1555 
1556 static inline bool tcp_write_queue_empty(struct sock *sk)
1557 {
1558         return skb_queue_empty(&sk->sk_write_queue);
1559 }
1560 
1561 static inline void tcp_push_pending_frames(struct sock *sk)
1562 {
1563         if (tcp_send_head(sk)) {
1564                 struct tcp_sock *tp = tcp_sk(sk);
1565 
1566                 __tcp_push_pending_frames(sk, tcp_current_mss(sk), tp->nonagle);
1567         }
1568 }
1569 
1570 /* Start sequence of the skb just after the highest skb with SACKed
1571  * bit, valid only if sacked_out > 0 or when the caller has ensured
1572  * validity by itself.
1573  */
1574 static inline u32 tcp_highest_sack_seq(struct tcp_sock *tp)
1575 {
1576         if (!tp->sacked_out)
1577                 return tp->snd_una;
1578 
1579         if (tp->highest_sack == NULL)
1580                 return tp->snd_nxt;
1581 
1582         return TCP_SKB_CB(tp->highest_sack)->seq;
1583 }
1584 
1585 static inline void tcp_advance_highest_sack(struct sock *sk, struct sk_buff *skb)
1586 {
1587         tcp_sk(sk)->highest_sack = tcp_skb_is_last(sk, skb) ? NULL :
1588                                                 tcp_write_queue_next(sk, skb);
1589 }
1590 
1591 static inline struct sk_buff *tcp_highest_sack(struct sock *sk)
1592 {
1593         return tcp_sk(sk)->highest_sack;
1594 }
1595 
1596 static inline void tcp_highest_sack_reset(struct sock *sk)
1597 {
1598         tcp_sk(sk)->highest_sack = tcp_write_queue_head(sk);
1599 }
1600 
1601 /* Called when old skb is about to be deleted (to be combined with new skb) */
1602 static inline void tcp_highest_sack_combine(struct sock *sk,
1603                                             struct sk_buff *old,
1604                                             struct sk_buff *new)
1605 {
1606         if (tcp_sk(sk)->sacked_out && (old == tcp_sk(sk)->highest_sack))
1607                 tcp_sk(sk)->highest_sack = new;
1608 }
1609 
1610 /* Determines whether this is a thin stream (which may suffer from
1611  * increased latency). Used to trigger latency-reducing mechanisms.
1612  */
1613 static inline bool tcp_stream_is_thin(struct tcp_sock *tp)
1614 {
1615         return tp->packets_out < 4 && !tcp_in_initial_slowstart(tp);
1616 }
1617 
1618 /* /proc */
1619 enum tcp_seq_states {
1620         TCP_SEQ_STATE_LISTENING,
1621         TCP_SEQ_STATE_OPENREQ,
1622         TCP_SEQ_STATE_ESTABLISHED,
1623 };
1624 
1625 int tcp_seq_open(struct inode *inode, struct file *file);
1626 
1627 struct tcp_seq_afinfo {
1628         char                            *name;
1629         sa_family_t                     family;
1630         const struct file_operations    *seq_fops;
1631         struct seq_operations           seq_ops;
1632 };
1633 
1634 struct tcp_iter_state {
1635         struct seq_net_private  p;
1636         sa_family_t             family;
1637         enum tcp_seq_states     state;
1638         struct sock             *syn_wait_sk;
1639         int                     bucket, offset, sbucket, num;
1640         kuid_t                  uid;
1641         loff_t                  last_pos;
1642 };
1643 
1644 int tcp_proc_register(struct net *net, struct tcp_seq_afinfo *afinfo);
1645 void tcp_proc_unregister(struct net *net, struct tcp_seq_afinfo *afinfo);
1646 
1647 extern struct request_sock_ops tcp_request_sock_ops;
1648 extern struct request_sock_ops tcp6_request_sock_ops;
1649 
1650 void tcp_v4_destroy_sock(struct sock *sk);
1651 
1652 struct sk_buff *tcp_gso_segment(struct sk_buff *skb,
1653                                 netdev_features_t features);
1654 struct sk_buff **tcp_gro_receive(struct sk_buff **head, struct sk_buff *skb);
1655 int tcp_gro_complete(struct sk_buff *skb);
1656 
1657 void __tcp_v4_send_check(struct sk_buff *skb, __be32 saddr, __be32 daddr);
1658 
1659 static inline u32 tcp_notsent_lowat(const struct tcp_sock *tp)
1660 {
1661         return tp->notsent_lowat ?: sysctl_tcp_notsent_lowat;
1662 }
1663 
1664 static inline bool tcp_stream_memory_free(const struct sock *sk)
1665 {
1666         const struct tcp_sock *tp = tcp_sk(sk);
1667         u32 notsent_bytes = tp->write_seq - tp->snd_nxt;
1668 
1669         return notsent_bytes < tcp_notsent_lowat(tp);
1670 }
1671 
1672 #ifdef CONFIG_PROC_FS
1673 int tcp4_proc_init(void);
1674 void tcp4_proc_exit(void);
1675 #endif
1676 
1677 int tcp_rtx_synack(struct sock *sk, struct request_sock *req);
1678 int tcp_conn_request(struct request_sock_ops *rsk_ops,
1679                      const struct tcp_request_sock_ops *af_ops,
1680                      struct sock *sk, struct sk_buff *skb);
1681 
1682 /* TCP af-specific functions */
1683 struct tcp_sock_af_ops {
1684 #ifdef CONFIG_TCP_MD5SIG
1685         struct tcp_md5sig_key   *(*md5_lookup) (struct sock *sk,
1686                                                 const struct sock *addr_sk);
1687         int             (*calc_md5_hash)(char *location,
1688                                          const struct tcp_md5sig_key *md5,
1689                                          const struct sock *sk,
1690                                          const struct sk_buff *skb);
1691         int             (*md5_parse)(struct sock *sk,
1692                                      char __user *optval,
1693                                      int optlen);
1694 #endif
1695 };
1696 
1697 struct tcp_request_sock_ops {
1698         u16 mss_clamp;
1699 #ifdef CONFIG_TCP_MD5SIG
1700         struct tcp_md5sig_key *(*req_md5_lookup)(struct sock *sk,
1701                                                  const struct sock *addr_sk);
1702         int             (*calc_md5_hash) (char *location,
1703                                           const struct tcp_md5sig_key *md5,
1704                                           const struct sock *sk,
1705                                           const struct sk_buff *skb);
1706 #endif
1707         void (*init_req)(struct request_sock *req, struct sock *sk,
1708                          struct sk_buff *skb);
1709 #ifdef CONFIG_SYN_COOKIES
1710         __u32 (*cookie_init_seq)(struct sock *sk, const struct sk_buff *skb,
1711                                  __u16 *mss);
1712 #endif
1713         struct dst_entry *(*route_req)(struct sock *sk, struct flowi *fl,
1714                                        const struct request_sock *req,
1715                                        bool *strict);
1716         __u32 (*init_seq)(const struct sk_buff *skb);
1717         int (*send_synack)(struct sock *sk, struct dst_entry *dst,
1718                            struct flowi *fl, struct request_sock *req,
1719                            u16 queue_mapping, struct tcp_fastopen_cookie *foc);
1720         void (*queue_hash_add)(struct sock *sk, struct request_sock *req,
1721                                const unsigned long timeout);
1722 };
1723 
1724 #ifdef CONFIG_SYN_COOKIES
1725 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1726                                          struct sock *sk, struct sk_buff *skb,
1727                                          __u16 *mss)
1728 {
1729         return ops->cookie_init_seq(sk, skb, mss);
1730 }
1731 #else
1732 static inline __u32 cookie_init_sequence(const struct tcp_request_sock_ops *ops,
1733                                          struct sock *sk, struct sk_buff *skb,
1734                                          __u16 *mss)
1735 {
1736         return 0;
1737 }
1738 #endif
1739 
1740 int tcpv4_offload_init(void);
1741 
1742 void tcp_v4_init(void);
1743 void tcp_init(void);
1744 
1745 /*
1746  * Save and compile IPv4 options, return a pointer to it
1747  */
1748 static inline struct ip_options_rcu *tcp_v4_save_options(struct sk_buff *skb)
1749 {
1750         const struct ip_options *opt = &TCP_SKB_CB(skb)->header.h4.opt;
1751         struct ip_options_rcu *dopt = NULL;
1752 
1753         if (opt->optlen) {
1754                 int opt_size = sizeof(*dopt) + opt->optlen;
1755 
1756                 dopt = kmalloc(opt_size, GFP_ATOMIC);
1757                 if (dopt && __ip_options_echo(&dopt->opt, skb, opt)) {
1758                         kfree(dopt);
1759                         dopt = NULL;
1760                 }
1761         }
1762         return dopt;
1763 }
1764 
1765 /* locally generated TCP pure ACKs have skb->truesize == 2
1766  * (check tcp_send_ack() in net/ipv4/tcp_output.c )
1767  * This is much faster than dissecting the packet to find out.
1768  * (Think of GRE encapsulations, IPv4, IPv6, ...)
1769  */
1770 static inline bool skb_is_tcp_pure_ack(const struct sk_buff *skb)
1771 {
1772         return skb->truesize == 2;
1773 }
1774 
1775 static inline void skb_set_tcp_pure_ack(struct sk_buff *skb)
1776 {
1777         skb->truesize = 2;
1778 }
1779 
1780 #endif  /* _TCP_H */
1781 

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